Hand-held power tools, for example, but not limited to, chainsaws, trimmers and hedgetrimmers are extensively used in garden and forestry applications. These power tools are required to be made compact and light weight for easy handling during operation. Typically, a power tool includes a power source which is drivably connected to a cutting device. Further, one or more handles are provided on the power tool to facilitate manual gripping during operation.
Typically, most of the power tools known in the art use a brush type DC motor as the power source. The brush type motor includes an electromagnetic rotor and a permanent magnet stator. During operation of the brush type DC motor, a brush assembly provides commutation between the rotor and the stator which is necessary for a continuous rotation of the rotor. Though, the power tools using the brush type DC motor are small and compact, the speed of the brush type DC motor is limited to a pre-determined range depending on the design and material of the brush assembly. Thus, these power tools typically utilize a gear assembly between the brush type DC motor and the cutting device.
The gear assembly not only increases the overall cost and weight of a power tool, but also the components of the gear assembly may require periodic maintenance and the overall running cost of the power tool increases. Further, an oil pump is provided to supply lubricant to the gear assembly and also to other moving parts of the power tools. Typically, the oil pump is driven by an auxiliary electric motor which further increases weight, running costs, and power and space requirements.
Moreover, in the brush type DC motor, the brushes may tend to wear out over a period of time due to constant friction and thus, need to be replaced periodically. This increases the maintenance requirements and requires regular disassembling of the power tool. Furthermore, at high speeds, the brush assembly may cause sparks during commutation, which is highly undesirable.
In light of the foregoing, there is a need for an improved method and system which addresses the above problems in a power tool, for example chainsaws, trimmers, hedgetrimmers etc.